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GEORGE D. VAN ARSIDALE, OF NEW YORK, N. Y.

ran-anon or MAKING acre ant rusoLnBLs runrantrc coinronnns.

No Drawing.

To all whom it may concern:

Be it known that I, GEORGE D. Vani ies- DALE, citizen of the'United States, residing at New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Methods of Making Acid and Insoluble illetallic Compounds, of which the following is a specification.

My present invention relates to that branch of chemistry known as hydrometallurgy and has for its primary object the provision of a method of treating metals, in solution, in such a manner that the reaction will produce, or precipitate, the dissolved metal as an insoluble, metallic salt, or compound and also produce, or form, free acid, whichmay later be employed in leaching out, or dissolving, more metals from their ores.

More specifically, my method consists-in the treatment of a solution of a salt of the metal to be precipitated, in the presence of a metal in metallic form, with a gaseous, or

dissolved gaseous, reducing agent, the resulting reaction precipitating the metal previously in solution and also forming free acid. This reaction is a more or less gen eral one and produces compounds varying with the metal, or metals, used and with the conditions under which the reaction takes place. Buttwo general conditions can be noted as essential to the effectiveness of this reaction, these being, that the-metal employed in the metallic state be such as to be acted upon by the reducing agent used, andthat the metal to be precipitated be such that its salt formed be insoluble, or at least with the use of the same metal, in the metallie state, as that metal whose insoluble salt or compound is to be precipitated.

In view of the above conditions, it will be understood that hereinafter, both in the specification and cl'aims,.when I refer to a metal, as the metal to be precipitated, this reference is intended to include only such metals as those which, when treatedby' the method. described, will form salts which are insoluble or partially insoluble in the acid produced that is metals whose sulfide are Specification of Letters Patent.

' Application filed June 25, 1914.-

Patented Aug. 223, 1916.

Serial I31 0. 847,349.

insoluble in dilute sulfuric acid. It will further be understood that. when I refer to a metal, as the'metal to be used in metallic state, I intend to include only such metals as will be acted upon by the reducing agent employed. Also hereinafter both in the specification and claims, when I refer to a reducing agent, this reference is intended to include only such reducing agents as are soluble and capable of acting upon themetal used as a precipitant.

Although other reducing agents maybe employed, 1 have found sulfur dioXid to be the most satisfactory, and this may be used either in the gaseous form or in solution.

l/Vl'1ere'sulfur dioxid'is employed as the reducing agent, the results of the reaction may be expressed by the following equation in which M80 represents a sulfate of the metal M to be precipitated and N another metal, in the metallic state:

'fids, may be formed.

It is obvious thata reaction, such as that expressed by the above formula may be made use of in a large number of ways. An example of its application is its use in the extraction of copper from ores.

- The following formulas represent the re actions taking place upon treatment of copper sulfate solutions and copper chlorid solutions with sulfur dioXid in the presence of These reactions may be applied in a number of ways in the hydrometallurgy ofcop- 2 v Lineman roasted if necessary and the copper afterward obtained in solution, usually by an acid solvent. There are several methods of precipitating the copper from such solutions, the most generally used heretofore, being its separation by metallic iron. In practice, however, this method has several disadvantages, among them being the fact if amount theoretically necessary for its pre-,

cipitation.

By making use of the herein described reaction in precipitating copper, with iron, in the presence of sulfur dioxid, a copper precipitate may be obtained uncontaminated by basic iron salts and the remaining liquors may be subsequently used for leaching additional copper ores, the formation of sulfuric acid being sutlicient in some cases to render the addition of fresh acid unnecessary. The amount of metallic iron needed for the complete precipitation of the copper will also, in most cases be reduced.

The best form of iron for precipitation is that kind having a large surface, such as old cotton ties, tin can scrap, and the like. However, large pieces of scrap iron can be used in this method, to greater advantage than in the ordinary methods of precipitation'of copperby metallic iron. This is-due to the fact that precipitated copper obtained by the ordinary methods is more or less adherent, therefore gathering upon the iron employed and rapidly reducing its effectiveness, making frequent; cleaning necessary and also necessitating the employment of long launders. On the other hand, the copper 'sulfid precipitate obtained by the employment of my method is not adherent and does not, therefore, reduce the efiiciency of the iron.

It is apparent that the method as described constitutes one step of a cycle of operations in the wet extraction of copper from its ores. Several examples of its use as such a step are as follows: For example the copper from mine waters may be precipitated by this reaction. For this it is, of course, necessary to have a source of supply of sulfur dioxid gas. If the work is being carried on near a smelter where roastin" is done, the gases from the roasters may be used, but where such gas is not available, it

may be obtained by roasting pyrites or other sulfids. If large amounts of Waste gases, or

'forc being passed into the solution.

part of my present invention.

of pyrites, are available, the method may be economically employed for treating comparatively dilute copper solutions. Assuming a supply of sulfur dioxid, the gas is broughtiuto contact with the copper solution to be treated, it being of course understood that if the gas is derived directly from roasters it should be passed through some suitable dust catching apparatus be This will not only cleanse the gas, but also somewhat lower its tenq'ierature. Solution of sulfur dioxid in the copper liquor may be eiiectwl in any suitable manner, such as by the use of a tower absorbing apparatus, the construction and operation of which is Well known and neednot bedescribed. The solution, after bein treated with the sulfur dioxid, is then brought into contact with metallic iron, the result being the precipitation of the copper as'copper sulfid and the formation of free sulfuric acid in the solution. In. case the precipitation of copper is not complete, heat should be applied. This may be done by utilization of waste steam or, if preferred, by blowing hot roaster gases, containing, sulfur dioxid ,directly into the solution without previously cooling them. Operating in this way, the reaction may take place without actual solution of the gas in appreciable quantities and the first anillast steps of the prmess united. After precipitation of the copper, the copper sulfid may be separated from the acid liquor in any one of a number of well known ways, this separation forming no The liquor from which. the copper has been separated, will contain more or less free sulfuric acid and may, therefore, be used for dissolving copper from ores.

Another example of the use of the reaction is as a modified step of the Huntand Douglas method.

By this method cuprous.

chlorid is precipitated from chlorid solutions simultaneously with the regeneration of free acid for leaching, by the injection. of sulfur dioxid gases, while the solution is heated, or by heating the solution after the injection of such gases, the precipitated cuprous chlorid being then treated in one of a number ways to obtain metallic copper. By the Hunt and Douglas method,

any silver present in the solution is not precipitated with the copper, but must be recovered from solution subsequently. In ap plying my reaction as a modification of the Hunt andv Douglas method, metallic iron may be used either to treat the precipitated cuprous chlorid in the presence of sulfur dioxid, or by heating a solution containing chlorid of copper with sulfur dioxid in the presence of metallic iron, the'result in either case being the formation of insoluble copmos ics.

per sulfid and free acid. lhe resulting copper precipitate is then separated from the any silver present in the solution will ,be

precipitated or separated out with the copper. In addition to the above examples,

, method may be applied for the precipitation of copper from solutions obtained by leaching ores with sulfuric acid, and in this case the resulting acid liquor is used as a part of the solvent for the fresh ores and the necessary. amount of acid to be supplied thereby considerably reduced. The reaction may also be used in cases where an ore is" prepared forlea-ching by a preliminary sulfatizing roast. By precipitating the copper from solutions obtained by leaching such sulfatiz ed ores, itis possible to -regenerate s'uiiicient acid to dissolve that portion of the copper in the roasted ore, which is not solilble in "Water.

Other examples of possible use of the method willsuggest themmlves to those fa- Iniliar with .ue'subj'ect. I

Although. l have as yet explained my method only in connection with the separation of copper from copper solutions, it will of course be understood that the examples thus far given are merely illustrative and that the method may be, employed in separating other metals and for other purposes under varying conditions. Therefore,

it will be appreciated that the equations given previously, are illustrative only and may, in some cases, represent only a part of, or the final results of the reactions. 1 do not wish. at all to limit myself to the em ployment of the method with any particular metal or metals and reserve the right to employ-it as it may prove applicable. For example, if'a solution containing sulfate of zinc, in which some sulfur dioxid hasbeen dissolved, is heated with metallic zinc, a part ofthe ain'cis precipitated as zinc sulfid and free sulfuric acid is formed, complete precipitation being prevented by the solu- This re action is represented by the following formula and serves to illustrate the fact that under somecircumstances, a metal may be precipitated from its solution, by my method, by the employment of the same metal in metallic form.

Again it is possible, with my method, to

precipitate an insoluble compound of a more electro-positive metal by one less electropositive. lhus, for example, a compound of zinc may be precipitated by iron as follows:

It must be borne in mind, however, that the reaction, represented by thegeneral formula first given, will not take place as de scribed whenv the product from the salt of the metal is readily soluble in the acid pro} duced. .Thus, if a solution of ferrous sulfate containing sulfur dioxid is heated with metallic iron, no metallic-compound is precipitated, since sulfid of iron is readily sol- 'uble in dilute sulfuric acid. Also aluminum arate metal compounds from'solutions con-.

taining iron alumina when such a result is desirable.

-Having thus described the invention, what is claimedas new is:

l.v The method of precipitating a metal from a solution of a saltof such metal, which consists in treating the solution with sulfur diorzid and bringing the solution so treated into contact with a metal in. metallic form. I v 9. The method of precipitating a metal from a solution of one of its salts, which consists intreating the solution with sulfur dioxid and bringing the solution so treated into contact with metalliciron.

3. The method of precipitating copper from a solution of one of-its saltsand of forming free acid, which consists in treating the copper solution with sulfur dioxid and in bringing the solution so treated into the presence of a metal in metallic form.

, 4. The method of precipitating copper from a solution of a salt of copper, which consists in treating the solution with sulfur dioxid and bringing'the solution so treated into contact with metallic iron.

.5. lhe method of precipitating copper from a copper chlorid solution, which consists in treating the solution with sulfur dioxid and bringing the solution so treated 8. The method of precipiisting copper in testimony whereof I aflix my signature from a solution of one of its salts, which in presence of two Witnesses. consists in treating the solutim with sulfur GEORGE E). VAN ARSDALE. [Ii- 5.} I dioxid and in bringing the solution so Witnesses: 5 treated into Contact with another metal in A. D. BROWN,

metallic form. F. F. BEST. 

